CFC (Chlorofluorocarbon)-based refrigerants or HCFC (Hydrochlorofluorocarbon)-based refrigerants have conventionally been used for refrigeration systems with a refrigerant circuit through which refrigerant circulates to operate on a vapor compression refrigeration cycle, such as air conditioning systems. The CFC-based and HCFC-based refrigerants, however, cause environmental problems, such as ozone layer depletion. It is therefore desired to renew such existing refrigeration systems into newer refrigeration systems using HFC (Hydrofluorocarbon)-based refrigerants or HC (Hydrocarbon)-based refrigerants.
Refrigerant pipes for connecting between a heat source unit and a heat use unit are often buried in structures such as buildings. Therefore, in such cases, it is difficult to change refrigerant pipes in renewing a refrigeration system. In these cases, to reduce the installation work period and cost, a new refrigeration system is installed by using the existing refrigerant pipes as they are.
Foreign materials, such as refrigeration oil for refrigeration systems using CFC-based or HCFC-based refrigerant containing chlorine, remain in the existing refrigerant pipes. Naphthenic mineral oil is mainly used as conventional refrigeration oil. If the naphthenic mineral oil is left and deteriorated in the refrigerant pipes, the expansion valves and other elements in the pipes may be corroded by chlorine ions or acids contained in the deteriorated mineral oil.
Therefore, before a new refrigeration system is installed and undergoes a trial run, it is necessary to clean the existing refrigerant pipes to remove residual foreign materials such as refrigeration oil.
A refrigeration system including a refrigerant circuit capable of a cleaning operation for the existing refrigerant pipes is disclosed, for example, in Japanese Unexamined Patent Publication No. 2001-41613. The refrigeration system includes a refrigerant circuit formed by connecting a heat source unit mainly including a compressor and a heat source side heat exchanger to an indoor unit having a heat use side heat exchanger via existing connecting pipes. A pipe on the suction side of the compressor is provided with oil recovery equipment for separating foreign materials such as refrigeration oil from refrigerant and recovering them.
After filled with HFC-based refrigerant, the refrigeration system activates the compressor to operate in cooling mode or heating mode so that the existing connecting pipes are cleaned by refrigerant circulating through the refrigerant circuit to collect foreign materials, such as refrigeration oil, into the oil recovery equipment.